US3739128A - Flame proof thermostat box - Google Patents

Abstract

A flame proof box to contain any one of several commercially available thermostat switches with a readily removable strap support for the switch; readily removable flame-proof means to conduct the wires and the capillary tube of the thermostat through the walls of the box; and a flame-proof means through the removable cover of the box for adjustment of the thermostat, that has a lost motion, positive-connection, clutch device that enables the cover to be secured in place and the clutch elements to be interengaged without pre-alignment of the clutch elements.

Description

United States Patent [191 Kaesser et al.

[ June 12, 1973 FLAME PROOF THERMOSTAT BOX [75] Inventors: Glenda F. Kaesser, St. Louis;

Marshall G. Zavertnik, Manchester, both of Mo.

[73] Assignee: Killark Electric Manufacturing Company, St. Louis, Mo.

[22] Filed: Sept. 30, 1971 [21] Appl. No.: 185,319

[52] US. Cl. 200/168 G, 337/380 [51] Int. Cl. ,H01h 21/08 [58] Field of Search 200/168 G; 337/112,

[56] References Cited UNITED STATES PATENTS 3,265,848 8/1966 Reik 200/168 G 3,385,945 5/1968 Tums 200/168 G 2,345,757 4/1944 Lester ZOO/168 G 5/1941 Bissell 200/168 G 8/1966 Farina et al 200/168 G X Primary Examiner-Robert K. Schaefer Assistant Examiner-William J. Smith AttorneyRogers, Ezell, Eilers & Robbins [5 7] ABSTRACT A flame proof box to contain any one of several commercially available thermostat switches with a readily removable strap support for the switch; readily removable flame-proof means to conduct the wires and the capillary tube of the thermostat through the walls of the box; and a flame-proof means through the removable cover of the box for adjustment of the thermostat, that has a lost motion, positive-connection, clutch device that enables the cover to be secured in place and the clutch elements to be interengaged without prealignment of the clutch elements.

13 Claims, 7 Drawing Figures FLAME PROOF THERMOSTAT BOX BACKGROUND OF THE INVENTION A primary purpose of the invention is to overcome prior art requirements of a different box for each thermostat switch, by providing a single box that, with simple selection of a few auxiliary parts, can be used with any of several commercially available thermostats. The basic box is uniform, and it can receive any of several switch-supporting straps shaped to be attached to the box by uniform attaching means, usually screws, in a manner to hold the particular switch in place in the box with its adjustment shaft in a predetermined position relative to the box that is the same for all switches.

Additionally there are uniform, flame-proof fittings to conduct the switch wires as well as the capillary tube through the walls of the box, that can be easily adapted by choice of auxiliary fittings, to accommodate various sizes and arrangements of wires and capillaries.

There is also a position clutch arrangement that has interlocking parts between the box cover and the thermostat adjusting shaft that can be adapted to the particular thermostat by a simple threaded adjustment, and the substitution of a simple auxiliary part proper for the selected thermostat.

This clutch arrangement has a further advantage that, though flame-proof and though requiring position interlocking of parts on the cover and parts fixed in the box, the interlocking parts are constructed to enable the cover to be fastened onto the box without prealignment of the clutch elements, which can thereafter be interlocked and maintained in interlocking position by a simple operation of the adjusting member outside the box.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the device;

FIG. 2 is an enlarged vertical section on the line 22 of FIG. 1;

FIG. 3 is a top view of the box with the cover removed;

FIG. 4 is an enlarged diametrical section through the thermostat adjustment connection;

FIG. 5 is a bottom view of a portion of the thermostat adjustment connection taken on the line 5-5 of FIG.

FIG. 6 is a diametrical section of a portion of the thermostat adjustment connection taken at right angles to the showing of FIG. 4 and on the line 6-6 thereof; and

FIG. 7 is a plan view of a connecting element for the thermostat adjustment.

DESCRIPTION OF THE PREFERRED EMBODIMENT This box 10 is designed to meet the requirements of explosion-proof receptacles. It has a bottom wall 11, end walls 12 and 13, side walls 14 and 15 with inwardly projecting flanges 16 around the top edges of these side and end walls. There is a cover 18 that can be attached or removed from the box. The cover is held in place by four screws 19 that can be threaded into screw holes 20 in the corners of the box. The flange 16 at the top is oppositely recessed at 24 and 25 to provide ledges for a purpose to be described.

Adjacent the bottom the box may have ears 27 and 28 through which holes may be provided to receive bolts or screws for attachment of the box to a support. In the preferred form, the box is cast metal, for example, aluminum. The interfaces between the cover and the box are ground smooth so that when the enclosure is assembled a 0.0015 inch feeler gauge will not enter the joint between the box and cover more than oneeighth of an inch.

Within the box a U-shaped thermostat mounting strap 30 has outwardly turned ends engaging the ledges within the recesses 24 and 25 and secured thereto by screws 31. This strap is of a size appropriate to mount a thermostat 33, here illustrated as being secured below the strap by screws 34. The box is of a size that can accommodate any of a number of regular commercial thermostats when a strap 30 appropriate thereto is provided. Each of these thermostats has an adjusting shaft 37, and the straps are sized and shaped so that shafts of all of the different thermostats will project toward a particular spot inside the cover 18. The rotation of the shaft 37 backward or forward adjusts the thermostat in the known manner.

The shaft 37 may be provided with a flat side for connection with a rotating knob or the like. In the event that the thermostat contains a socket instead of a shaft 37, the shaft 37 is a stub shaft provided with means to engage into the thermostat and to return the adjusting members thereof.

The present invention provides flame-proof connecting means leading through the cover of the box to provide for adjustment of the thermostat from outside the box. To this end the cover of the box has a tapped opening medially through it which receives a fitting 40 threaded into the proper position and locked into place by a nut 41. The threads are long enough and tight enough to meet flame-proofing standards.

Through the axis of this fitting 40 there is a smooth bored hole that receives with a close fit a smooth shaft somewhat longer than the thickness of the fitting. These parts are made long enough and with close enough fits to meet flame-proof standards. The shaft 42 is grooved at its ends to receive snap-in rings 43 and 44. These snap rings 43 and 44 are spaced apart a distance to permit a limited axial movement of the shaft 42 through the fitting 40. A kerf 45 or other equivalent means such as a knob is provided in the outer end of the shaft 42 to permit the shaft to be adjusted by rotat- The inner end of the shaft receives a conical coil spring 48 that is held in place under compression by a removable collar 49. This collar may have set screws, as illustrated, to hold it in place but to permit it to be removed. The collar 49 has a cross pin 50 integrally attached to its under side, as by welding. The coil spring 48 urges the shaft inwardly of the box but permits a resilient displacement of the shaft outwardly, all of this movement being within the limits provided by the two spring rings 43 and 44.

The thermostat adjusting shaft 37 likewise has a collar 54 secured to its outer end as by set screws. The collar 44 has a cross pin 55 integrally attached to its upper end as by welding.

An interconnecting, oppositely slotted clutch elementor connector 56, here shown as being made of an electrically insulating plastic material, is interposed between the collars 49 and 54. This connector 56 has transverse slots 57 and 58 in its upper and lower surfaces, respectively, that are of a size to receive the two cross pins 50 and 55 of the collars 49 and 54.

When the connector 56 is in place between the two collars 49 and 54, the cross pins 50 and 55 normally are in their respective slots of the connector 56, so that rotation of the externally projecting shaft 42 is transmitted by a positively driven interconnection through the connector 56 to cause rotation of the thermostat adjusting shaft 37.

Thermostats of the present kind are controlled by bulbs 60 located at the point at which the temperature is to be regulated. The bulb 60 is connected by a capillary tube 61 into the thermostat in a manner known in the art.

In the present box, a fitting is provided to insure that the capillary is introduced into the box without permitting transmission of flame through the wall of the box, and yet in a manner to permit the thermostat to be removed at will through the top opening of the box without cutting the capillary tube. To this end the wall 13 is drilled and tapped to receive a nipple 70 that is threaded through the wall in such a fashion as to prevent transmission of flame. The interior of the fitting 70 is of a smooth, tapered contour and it receives two identical semi-conical members 71 of the same taper, that can be fitted together to form a full frustum of a cone.

Each of the semi-conical members 71 is provided with a semi-cylindrical axial groove 72 extending from end to end of the members, and a projecting semicylindrical boss or projection 73. When the two semiconical members 71 are placed together, forming the full frustum of a cone, the two semi-cylindrical grooves 72 provide a cylindrical hole that fits closely about the capillary tube 71, and the two bosses 73 form a cylindrical projection on the outer end of the cone. A cap nut 74 is threaded over the two members 71 and onto the fitting 70. As shown, it has a hole which receives two bosses 73 thereby aiding in centering the cone, and when the cup is threaded onto the nipple 70, it presses the two members of the cone into the complementary conical surface of the fitting 70. This inward pressure forces the two members together so that their interfaces are in a snug relationship and so that they engage about the capillary tube 61 with a snug fitting. The surfaces are finished and sized so as to prevent the transmission of flame between the inside and the outside of the box in any way through the fitting. The cap nut 74 can be secured in position by a lock screw as is indicated.

Commercial thermostats of this type have two different kinds of lead. Some have terminals within the box to which leads are brought through the wall of the box and connected. These leads may be carried through the box will in a fitting in which they are plotted in a conventional fashion, since they can stay permanently in the box. However, there are commercial thermostats which are provided with longer leads permanently connected internally to the thermostat, and which must be carried through the wall of the box and connected outside the box. To remove this type of thermostat from the box, these leads must be withdrawn through the wall of the box. The present box accommodates these without requiring destruction of the potting.

The box is drilled and tapped through the end 12, and a tubular externally threaded fitting 80 is secured in the opening in such a manner as to prevent transmission of flame through the threaded portion. The fitting 80 is provided with external threads on its outer end so that it can be connected in flame-proof manner with a regular conduit.

The fitting 80 has a smooth cylindrical inner surface to receive an equally smooth cylindrical or tubular member 82. This member can be held in place by snap rings 83 and 84 on its opposite ends, preferably allowing some free endwise play. Wires 85 pass through the tubular fitting 82 and are potted in place as by potting compound 86 against an electric washer 87. A strip of tape 88 may confine the wires to the bracket and the thermostat 33.

USE

In use, the thermostat 33 is mounted on the strap 30 by the screws 34. By simply selecting the proper U- strap 30 suitable to the made of thermostat at hand, the user may mount any of several commercial thermostats in this one sized box. All of the straps dispose screw holes to receive the screws 31. All dispose the adjusting shafts 37 to be axially aligned with the shaft 42 in the cover 18.

If the lead-in wires 85 are as shown, they are passed through the tube or sleeve 82 and are potted therein by the positioning compound 86, which completely seals the tube against transmission of flame through it. This potting compound can be applied either before or after the thermostat is assembled in the box. Obviously only one sized sleeve may be provided, as it is large enough for all thermostat wire combinations. But to reduce the cross section of potting compound, a sleeve with smaller internal diameter and the same external diameter may be used without requiring a change in the fitting 80. The sleeve 82, with the snap ring 83 removed, is inserted into the fitting 80, and the snap ring 83 put into its groove on the outer end of the sleeve, so that the sleeve is confined against withdrawal. The fit between the outer wall of the sleeve and the fitting 80 is such that it will inhibit the transmission of flame through the wall 12.

The thermostat bulb must be passed through the wall 13 when the thermostat 33 is installed in the box. The small end of the conical fitting is large enough to pass any of the standard bulbs. After the bulb is thus passed through the fitting 70, the capillary 61 is drawn as straight as can be done easily, and the two semiconical members 71, selected to provide the proper axial hole diameter for the particular thermostat capillary, are placed around the capillary 61 with the notches 72 embracing it. The members 71 are then pushed by hand into the fitting 70 and the cap nut 74 screwed into place. The cap nut drives the two members 71 together so that their interfaces are in close association and so that the two grooves 72 closely embrace the capillary 61, all with fits of adequate length and closeness to prevent transmission of flame through the wall 10. The final straightening out of the capillary within the hole through the members 71 is produced by the squeezing action of the members.

The cap nut 74 is turned down tightly enough to insure the foregoing, and may be held against becoming loose by a set screw as indicated.

With the wires 85 in place in the fitting and the capillary 61 in the fitting 70, 'as described, the ends of the strap 30 are screwed down by the screws 31 to secure the thermostat in the box. When it is desired to remove the thermostat for servicing or replacement, it is necessary to remove the screws 31, loosening the strap that supports the thermostat, to remove the cap nut 74 and the two conical wedges 71 from about the capillary 61, and to spring the retaining ring 83 from the tube 82, freeing it and the wires 85 (provided their external junctions have been disconnected). Then the strap, with thermostat, wires, and bulb can be removed from the box.

A particular feature of this application resides in the manner in which the adjusting means is made that permits the quick application of the cover 18 to the box 10. An appropriate collar 54 is secured onto the thermostat shaft 37, and the connector 56 is placed onto the collar 54 with the notch 58 over the cross pin 55. The cover 18 is prepared by attaching a collar 49 of appropriate inside diameter to the shaft 42, and loosening the nut 41 and screwing the fitting in or out of to an estimated position suitable to permit the interlock of the bar into the slot 57 of the connector 56 when the shaft 42 is displaced outwardly against the spring 48, and the cover 18 is in attached position. The lock nut 41 is tightened to maintain this relationship. The cover 18 with the screws 19 loose, is placed into its proper position on the box.

When the cover is put into place, the upper cross pin 50 may not be rotated into position to fit into the slot 57. The cover may nevertheless be pressed down into position and the screws 19 at least partially engaged with the appropriate holes in the box. With the pin 50 out of registry with the slot 57, the shaft 42 is displaced outwardly, further compressing the spring 48, this being permitted by the spacing of the snap ring 44. Preferably, this snap ring permits enough outward movement of the shaft 42 to permit the cover to be placed down against the box even though the pin 50 is out of registry with the slot 57.

With this situation, the shaft 42 is rotated. As soon as the pin 50 registers with the slot 57, it will be snapped into place therein under the action of the spring 48 and will be held in such disposition by the fact that the spring remains partly under compression. Thereupon, the screws 19 may be turned firmly into engagement and the mechanism will be retained in this position. Thus, it is not necessary to provide a careful prealignment and retaining of parts in pre-aligned position in the assembly of the thermostat in the box.

The description has referred to a thermostat, as this uses most of the features of this invention. Other devices having like rotary adjusting means may be installed in such a box. If they have wiring or tubular projections or other equipment like those things, they may take advantage of the other features of the assembly, to wit, the potting compound fitting and the capillary tube fitting. Accordingly, in a broader sense, the enclosed device is referred to as one responsive to changes in physical conditions, and in a specific and optimum sense, as a thermostat. In all cases, the assembly provides an enclosure for an externally adjustable device having portions that must extend outside the enclosure, wherein the adjustment, as well as the passages to the outside, are all flame-proof.

Various changes and modifications may be made within this invention as will be readily apparent to those skilled in the art. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

What is claimed is:

1. In a box to receive and mount any one of a plurality of mounted devices responsive to physical conditions, each having an adjusting member turnable back and forth; means to secure a mounted device removably in the box with its adjusting member in a predetermined position with respect to a wall of the box, adjusting means mounted in the wall of the box including a positive-engagement clutch, an axially compressible means, and a rotatable shaft passing through the said wall, the means to secure the mounted device in the box disposing the adjusting member thereof in interconnectable position relative to the adjusting means, the fit of the rotatable shaft and the length of its interengagement with the wall being such that flame passage through the wall is retarded, the positive-engagement clutch comprising axially separable interengageable elements axially movable together into engagement, the axially compressible means urging them into engagement, but permitting disposition of the mounted device in fixed position with respect to the wall with them in an abutting disengaged position, rotation of the shaft from outside the wall then aligning the parts whereupon the yieldable means causes them to become interengaged so that they are clutched together and so that rotation of the shaft thereafter rotates the adjusting member.

2. In the box of claim 1: the axially compressible means comprising the rotatable shaft and a mounting therefor through the wall permitting limited axial displacement of the shaft, and spring means urging the shaft inward of the box to effect engagement of the clutch, the mounting providing interfitting surfaces of closeness and length to retard transmission of flame between inside and outside of the box.

3. In the box of claim 1: a mounting for the shaft in the wall having a member holding the shaft for its axial and rotary movement, the member being secured to the wall for adjustment into and out of the wall, means limiting axial movement of the shaft in the member, the axial adjustment providing predetermined initial positioning of the shaft, and the connection of the member in the wall having closeness and length to retard flame transmission.

4. In the box of claim 3: the member being threaded into the wall, and lock means to hold it in adjusted position in the wall.

5. In the box of claim 1: the wall being separable from the box, and disconnectable attaching means for removably securing the wall onto the box, the axially compressible means permitting the wall to be positioned and connected to the box without prior interengagement of the clutching elements.

6. In the box of claim 1: the means to secure the mounted device in the box comprising a removable element having prepositioned attaching means with the box so that other removable elements with like attaching means but different attachments to hold the mounted device may be attached, to dispose different mounted devices with their adjusting members in predetermined position for interengagement with the same adjusting means on the box wall.

7. In the box of claim 1: the clutch including two collars, one on the rotatable shaft, the second on the adjusting member of the mounted device, both being removable, and means for effecting driving interengagement between them, the means having positive drive interfitting components.

8. In the box of claim 7: the last named means including a connector between the two collars, and projection and socket means between each collar and the connector.

9. In the box of claim 1: the mounted device being a thermostat.

10. In the box of claim 9: the thermostat having a casing and an enlarged sensing element spaced from the casing and connected into it by a thin elongated memher; the box having an opening through a wall large enough to permit the sensing element to pass through, and having means fitting into the opening and engaging the thin elongated member, the said means having engagement with the box and with the thin member of length and closeness to retard flame passage.

11. In the box of claim 10: the thermostat having wiring, and the box having a hole through a wall through which the wiring can pass; and means engaged in the hole and about the wiring and removably engaged in the hole through the wall, the said means having en-' gagement with the wiring and through the wall of length and closeness to retard passage of flame.

12. In a box to receive and mount a thermostat having a casing, an adjusting member, a sensing bulb connected into the casing by a capillary tube, and wiring connected into the casing; the box having an adjusting means through a wall connectable with the adjusting member of the thermostat, including a movable adjusting member having a fit close and long enough to retard flame passage; the box having a wall opening large enough to pass the bulb, and removable means engageable therein and removably engageable with the capillary tube with a fit close and long enough to retard flame; one wall of the box being removable to withdraw the thermostat when the removable means engaging the capillary is removed from the box and from the capillary tube.

13. In the box of claim 12: the thermostat having wiring, and the box having a wiring opening through a wall, a tubular element about the wiring with sealing material molded in the tubular element about the wiring; means engaging the tubular element in the wall with a closeness and length to retard flame, the said means being removable with the wires and sealing material.

Claims (13)

1. In a box to receive and mount any one of a plurality of mounted devices responsive to physical conditions, each having an adjusting member turnable back and forth; means to secure a mounted device removably in the box with its adjusting member in a predetermined position with respect to a wall of the box, adjusting means mounted in the wall of the box including a positive-engagement clutch, an axially compressible means, and a rotatable shaft passing through the said wall, the means to secure the mounted device in the box disposing the adjusting member thereof in interconnectable position relative to the adjusting means, the fit of the rotatable shaft and the length of its interengagement with the wall being such that flame passage through the wall is retarded, the positive-engagement clutch comprising axially separable interengageable elements axially movable together into engagement, the axially compressible means urging them into engagement, but permitting disposition of the mounted device in fixed position with respect to the wall with them in an abutting disengaged position, rotation of the shaft from outside the wall then aligning the parts whereupon the yieldable means causes them to become interengaged so that they are clutched together and so that rotation of the shaft thereafter rotates the adjusting member.

2. In the box of claim 1: the axially compressible means comprising the rotatable shaft and a mounting therefor through the wall permitting limited axial displacement of the shaft, and spring means urging the shaft inward of the box to effect engagement of the clutch, the mounting providing interfitting surfaces of closeness and length to retard transmission of flame between inside and outside of the box.

3. In the box of claim 1: a mounting for the shaft in the wall having a member holding the shaft for its axial and rotary movement, the member being secured to the wall for adjustment into and out of the wall, means limiting axial movement of the shaft in the member, the axial adjustment providing predetermined initial positiOning of the shaft, and the connection of the member in the wall having closeness and length to retard flame transmission.

4. In the box of claim 3: the member being threaded into the wall, and lock means to hold it in adjusted position in the wall.

5. In the box of claim 1: the wall being separable from the box, and disconnectable attaching means for removably securing the wall onto the box, the axially compressible means permitting the wall to be positioned and connected to the box without prior interengagement of the clutching elements.

6. In the box of claim 1: the means to secure the mounted device in the box comprising a removable element having prepositioned attaching means with the box so that other removable elements with like attaching means but different attachments to hold the mounted device may be attached, to dispose different mounted devices with their adjusting members in predetermined position for interengagement with the same adjusting means on the box wall.

7. In the box of claim 1: the clutch including two collars, one on the rotatable shaft, the second on the adjusting member of the mounted device, both being removable, and means for effecting driving interengagement between them, the means having positive drive interfitting components.

8. In the box of claim 7: the last named means including a connector between the two collars, and projection and socket means between each collar and the connector.

9. In the box of claim 1: the mounted device being a thermostat.

10. In the box of claim 9: the thermostat having a casing and an enlarged sensing element spaced from the casing and connected into it by a thin elongated member; the box having an opening through a wall large enough to permit the sensing element to pass through, and having means fitting into the opening and engaging the thin elongated member, the said means having engagement with the box and with the thin member of length and closeness to retard flame passage.

11. In the box of claim 10: the thermostat having wiring, and the box having a hole through a wall through which the wiring can pass; and means engaged in the hole and about the wiring and removably engaged in the hole through the wall, the said means having engagement with the wiring and through the wall of length and closeness to retard passage of flame.

12. In a box to receive and mount a thermostat having a casing, an adjusting member, a sensing bulb connected into the casing by a capillary tube, and wiring connected into the casing; the box having an adjusting means through a wall connectable with the adjusting member of the thermostat, including a movable adjusting member having a fit close and long enough to retard flame passage; the box having a wall opening large enough to pass the bulb, and removable means engageable therein and removably engageable with the capillary tube with a fit close and long enough to retard flame; one wall of the box being removable to withdraw the thermostat when the removable means engaging the capillary is removed from the box and from the capillary tube.

13. In the box of claim 12: the thermostat having wiring, and the box having a wiring opening through a wall, a tubular element about the wiring with sealing material molded in the tubular element about the wiring; means engaging the tubular element in the wall with a closeness and length to retard flame, the said means being removable with the wires and sealing material.

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